The present invention relates to an improvement of a developing process of photographic materials such as photographic film, roll films, sheet films, photographic plates, photographic papers or the like.
The purpose of this invention is to solve the problem of poor uniformity in development to be formed, at the time of the developing process, on the sensitive materials namely on the opposite marginal areas of roll films and other photographic materials placed especially close to the top and/or bottom of development tanks.
For the above purpose the films are placed in the development tanks allowing spaces between the films and the top and/or bottom of the tanks in the course of the developing process.
Such poor uniformity in development is classified mainly into two kinds, one which has cloud-like patterns over the surface of the photographic materials and the other has narrow strip-like patterns at the opposite marginal areas of the photographic materials.
The formation of the former may be effectively prevented by sufficient agitation of the photographic materials for about 30 seconds at the beginning of developing process in a development tank, which treatment has been broadly employed in the current photographic development process. It has not been successful, however, to prevent the formation of the latter, narrow strip-like patterns, as the cause has not been found out.
The inventors of the present invention tried to find out the causes of the strip-like patterns by carrying out many tests. The developing is usually carried out by shaking the development tank as soon as the photographic sensitive materials have been placed in the tank and sufficient developing solution has been poured into the tank to wholly submerge the materials in the solution.
Thus, the photographic materials are exposed to the developing solution which flows upwardly and downwardly on the surface of the materials as a result of the shaking of the tank. Contrary to the above procedure, the inventors made an attempt to place the photographic materials supported on a holding frame into the tank already filled with the developing solution and then repeatedly move the holding frame to the bottom of the development tank. As the result of this attempt, it was found that the narrow strip-like patterns come out only in the downward marginal areas of the materials.
From this, it was found that such poor uniformity in development is caused by the vortical flow of the developing solution in contact with the surface of the materials which has been generated as the solution is pushed or carried by the downward movement of the holding frame or the materials as the frame hits the bottom of the tank and rebounds.
Essentially, the development advances more quickly when the contact of the developing solution with the photographic sensitive materials is active and, on the other hand, it becomes slow when the contact between the flow of developing solution and the photographic sensitive materials is less active. Thus, the poor uniformity is caused when the contact due to flow of the developing solution over the surface of the sensitive materials is not uniform.
It was also found out that the vortex flow of developing solution exists only in a zone of constant height from the bottom of the tank -- usually 10 to 25 millimeters. Therefore, uniform development of a sensitive material is expected if the placement of the material in this zone is avoided, or if a space of 10 to 25 millimeters is kept between the material and the bottom (and the top) of the tank during its reversing motion in the process of the development.